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排序方式: 共有177条查询结果,搜索用时 62 毫秒
81.
Jane Brown Marie A. Colucci Simon C. Hirst Jason J. Shiers Jonathan G. Williams 《Tetrahedron letters》2008,49(33):4968-4971
Functionalised silicas 2 and 3 are effective for the cation exchange SPE purification of basic molecules containing acid-sensitive functionalities, the selective separations of mixtures of basic compounds and accelerated reaction work-ups/product isolations. 相似文献
82.
Lainchbury MD Medley MI Taylor PM Hirst P Dohle W Booker-Milburn KI 《The Journal of organic chemistry》2008,73(17):6497-6505
A concise, linear synthesis of the Stemona alkaloid (+/-)-neostenine is reported. Key features include an organocopper-mediated bislactone C2-desymmetrization for the stereoselective construction of the cyclohexane-lactone C,D-rings. The assembly of the fused pyrrolo[1,2-a]azepine core was achieved by application of a [5 + 2] maleimide photocycloaddition. A custom FEP flow reactor was used to successfully overcome the scale limitations imposed by a classical immersion well batch reactor. The synthesis was completed in 14 steps from furan, in 9.5% overall yield, without the use of any protecting groups. 相似文献
83.
Jeffry L. Hirst 《Mathematical Logic Quarterly》1993,39(1):447-453
One of the earliest applications of transfinite numbers is in the construction of derived sequences by Cantor [2]. In [6], the existence of derived sequences for countable closed sets is proved in ATR0. This existence theorem is an intermediate step in a proof that a statement concerning topological comparability is equivalent to ATR0. In actuality, the full strength of ATR0 is used in proving the existence theorem. To show this, we will derive a statement known to be equivalent to ATR0, using only RCA0 and the assertion that every countable closed set has a derived sequence. We will use three of the subsystems of second order arithmetic defined by H. Friedman ([3], [4]), which can be roughly characterized by the strength of their set comprehension axioms. RCA0 includes comprehension for Δ definable sets, ACA0 includes comprehension for arithmetical sets, and ATR0 appends to ACA0 a comprehension scheme for sets defined by transfinite recursion on arithmetical formulas. MSC: 03F35, 54B99. 相似文献
84.
85.
A Self‐Assembled Respiratory Chain that Catalyzes NADH Oxidation by Ubiquinone‐10 Cycling between Complex I and the Alternative Oxidase
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Andrew J. Y. Jones James N. Blaza Hannah R. Bridges Benjamin May Anthony L. Moore Judy Hirst 《Angewandte Chemie (International ed. in English)》2016,55(2):728-731
Complex I is a crucial respiratory enzyme that conserves the energy from NADH oxidation by ubiquinone‐10 (Q10) in proton transport across a membrane. Studies of its energy transduction mechanism are hindered by the extreme hydrophobicity of Q10, and they have so far relied on native membranes with many components or on hydrophilic Q10 analogues that partition into membranes and undergo side reactions. Herein, we present a self‐assembled system without these limitations: proteoliposomes containing mammalian complex I, Q10, and a quinol oxidase (the alternative oxidase, AOX) to recycle Q10H2 to Q10. AOX is present in excess, so complex I is completely rate determining and the Q10 pool is kept oxidized under steady‐state catalysis. The system was used to measure a fully‐defined KM value for Q10. The strategy is suitable for any enzyme with a hydrophobic quinone/quinol substrate, and could be used to characterize hydrophobic inhibitors with potential applications as pharmaceuticals, pesticides, or fungicides. 相似文献
86.
Andrew R. Hirst Dr. Juan F. Miravet Dr. Beatriu Escuder Dr. Laurence Noirez Dr. Valeria Castelletto Ian W. Hamley Prof. Dr. David K. Smith Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(2):372-379
Two‐component systems capable of self‐assembling into soft gel‐phase materials are of considerable interest due to their tunability and versatility. This paper investigates two‐component gels based on a combination of a L ‐lysine‐based dendron and a rigid diamine spacer (1,4‐diaminobenzene or 1,4‐diaminocyclohexane). The networked gelator was investigated using thermal measurements, circular dichroism, NMR spectroscopy and small angle neutron scattering (SANS) giving insight into the macroscopic properties, nanostructure and molecular‐scale organisation. Surprisingly, all of these techniques confirmed that irrespective of the molar ratio of the components employed, the “solid‐like” gel network always consisted of a 1:1 mixture of dendron/diamine. Additionally, the gel network was able to tolerate a significant excess of diamine in the “liquid‐like” phase before being disrupted. In the light of this observation, we investigated the ability of the gel network structure to evolve from mixtures of different aromatic diamines present in excess. We found that these two‐component gels assembled in a component‐selective manner, with the dendron preferentially recognising 1,4‐diaminobenzene (>70 %), when similar competitor diamines (1,2‐ and 1,3‐diaminobenzene) are present. Furthermore, NMR relaxation measurements demonstrated that the gel based on 1,4‐diaminobenzene was better able to form a selective ternary complex with pyrene than the gel based on 1,4‐diaminocyclohexane, indicative of controlled and selective π–π interactions within a three‐component assembly. As such, the results in this paper demonstrate how component selection processes in two‐component gel systems can control hierarchical self‐assembly. 相似文献
87.
L. S. Hirst 《Liquid Crystals Today》2013,22(3):15-22
Resonant X-ray scattering is a relatively new technique in the field of liquid crystals and in recent years has been used to investigate the structures of the SmC* sub-phases. This work has been carried out on several materials which include either a sulfur or selenium atom and has revealed the detailed biaxial structure of the four layer intermediate (ferrielectric) phase. Resonant X-ray scattering has also been used to produce the first in-situ measurements of the chiral smectic sub-phases in a liquid crystal device. Both the antiferroelectric and the four-layer intermediate phases have been observed via this technique in a device geometry. Electric field studies have also been carried out in these phases whilst monitoring phase structure simultaneously. In this paper I will summarize the most up-to-date results from resonant scattering in free-standing films and discuss resonant scattering experiments on liquid crystal devices. 相似文献
88.
A. J. Hall K. Schwertassek G. Garkuscha K. M. Markuse A. W. Ssurowaja A. P. Sakonschtschikow D. I. Galperin D. I. Tumarkin J. Barritt H. H. Bowen F. L. Goodall A. Whitehead H. R. Hirst A. T. King M. Harris A. L. Smith T. A. Schmelewa und R. Hart 《Fresenius' Journal of Analytical Chemistry》1940,120(5-6):216-220
Ohne Zusammenfassung 相似文献
89.
Abrar Hussain James L. Melville Jonathan D. Hirst 《Journal of computer-aided molecular design》2010,24(1):1-15
Actin-binding natural products have been identified as a potential basis for the design of cancer therapeutic agents. We report
flexible docking and QSAR studies on aplyronine A analogues. Our findings show the macrolide ‘tail’ to be fundamental for
the depolymerisation effect of actin-binding macrolides and that it is the tail which forms the initial interaction with the
actin rather than the macrocycle, as previously believed. Docking energy scores for the compounds were highly correlated with
actin depolymerisation activity. The 3D-QSAR models were predictive, with the best model giving a q
2 value of 0.85 and a r
2 of 0.94. Results from the docking simulations and the interpretation from QSAR “coeff*stdev” contour maps provide insight
into the binding mechanism of each analogue and highlight key features that influence depolymerisation activity. The results
herein may aid the design of a putative set of analogues that can help produce efficacious and tolerable anti-tumour agents.
Finally, using the best QSAR model, we have also made genuine predictions for an independent set of recently reported aplyronine
analogues. 相似文献
90.
New ab initio potential energy surfaces for the (2)Pi ground electronic state of the Ar-SH complex are presented, calculated at the RCCSD(T)/aug-cc-pV5Z level. Weakly bound rotation-vibration levels are calculated using coupled-channel methods that properly account for the coupling between the two electronic states. The resulting wave functions are analyzed and a new adiabatic approximation including spin-orbit coupling is proposed. The ground-state wave functions are combined with those obtained for the excited (2)Sigma(+) state [D. M. Hirst, R. J. Doyle, and S. R. Mackenzie, Phys. Chem. Chem. Phys. 6, 5463 (2004)] to produce transition dipole moments. Modeling the transition intensities as a combination of these dipole moments and calculated lifetime values [A. B. McCoy, J. Chem. Phys. 109, 170 (1998)] leads to a good representation of the experimental fluorescence excitation spectrum [M.-C. Yang, A. P. Salzberg, B.-C. Chang, C. C. Carter, and T. A. Miller, J. Chem. Phys. 98, 4301 (1993)]. 相似文献